Electric Shower

For any certainty you will need an electrician to test the supply to the unit. That's the breaker, rcd, cable and switch. If all this is still good then the shower unit is to blame and needs to be replaced. It is unlikely that anyone but a qualified sparky will be able to make the above determination. Kind regards Martin

Depends on a few things how old is the shower? Can you get spares for it? It may be cost effective to repair it or it may be more economical just to replace it. Bear in mind if it is old and you don’t get the same unit the pipe work may need adjusting which would add to the cost.

Not necessarily it depends on the age of the shower if the shower is an old shower it may be that some of the internal components are starting to deteriorate and this is what's causing the breaker to trip it could also be a wiring fault or it could be a fault with the RCD itself, it's not uncommon with electric showers to find that the fault is with the isolation switch, it would be best to get an electrician out to assess the situation, carry out adequate testing and go from there.

I would check the isolation switch first it is very common for connections to burn out if not tight enough or being overloaded by the shower, it could be your shower kW is too high for the supply cable.

No as it may not be the unit itself but a fault with the wiring that supports the shower or a problem with the shower isolation switch. Call an electr before replacing the shower as it may not solve the problem